Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Chalfin Member of the Salem Limestone (Baxter, 1960a, p. 24-27) is named for the village of Chalfin Bridge, Monroe County.
The type section of the Chalfin Member is in the Mississippi River bluffs 1 mile southwest of the village of Chalfin Bridge (NE SW 7, 4S-10W), where the member is 39.5 feet thick.
Extent and Thickness
The Chalfin is 26-57 feet thick in the outcrop area.
The Chalfin consists of varying thicknesses of fine-grained limestone; fine- to medium-grained, fossiliferous, locally oolitic limestone; and semilithographic limestone, some of it brecciated. The lower 10 feet is predominantly a calcarenite composed of bryozoan detritus, crinoid columnals, microcrystalline pellets, and a few oolites.
Eoendothyranopsis group pressus-rarus, Koninckopora sahariensis, K. inflata, Septabrunsiina, and profuse Calcisphaera characterize the Chalfin.
BAXTER, J. W., 1960a, Salem Limestone in southwestern Illinois: Illinois State Geological Survey Circular 284, 32
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